I handed in my notice on my current employment due to work related stress and following a very frightening incident. I have been on sick leave through notice period due to work related stress and will do so for the remaining 3 weeks of my notice. During this time off I am much better as I know i will not be returning to this toxic work environment. I have been offered a new role in an unrelated field (health) and will not be subjected to the stresses and dangers I was in previous role. They are booking me in for shifts on weekends (my current employment is weekdays 9-5). If I went ahead I would do so only if my GP gave me the go-ahead that I was fit to start new role (and there is no reason why they should say I am not).
However, where does this leave me with my current employer? I am effectively off sick for job 1 until my notice period ends. I requested they allow me to reduce my notice period and leave early and they refused as they can't employ anyone. The hours I would work for new job would only be around 10 on weekends for the next two weekends. I would not take up the weekday and full time shifts until my contract with original employer ended.
Is this ok/legal?